Flex OS is built on top of CyanogenMod with some other features ported from other ROMs like Slim ROM and others.
Flex OS ROM features:
* FlexControl – All the tweaks and features in one place!
* Animation Control – Toast animations, Listview animations and system transitions.
* HeadsUp Customizations just like Cm11!
* Slim DSLV
* Navigation Bar Tweaks – On/Off Toggle, Dimensions
* Slim Advanced IME Features
* Statusbar Network Speed Meter
* Screen Sound Enable/Disable Toggle
* Camera Switch Sound Enable/Disable Toggle
* OmniSwitch – Use omniswitch alongside stock android recent apps or use it as primary.
* Recents FAB Button – Positions (Top left, Top right, Top center, Bottom left, Bottom right, Bottom center)
* LCD Density Adjuster
* Volume Steps
* Hide superuser icon in statusbar
* Double tap to sleep on navigation bar and status bar
* Instant reboot from power menu
* App Circle Sidebar
* Captive Portal – If disabled, a connection to google servers is not required in order to detect data connection.
* CyanogenMod Theme Engine
* Statusbar Clock Customization
* Volume Steps
* Inbuilt File Manager from OmniROM
* Quick pulldown
* Moar Material!
* Battery icon customization
*SlimPIE
* Statusbar Carier.
* Statusbar clock color.
* Statusbar clock font style.
* SlimPIE: Configurable sensitivity.
* SlimPIE: give user ability to reduce trigger heights if IME keyboard shows up.
* Ambient Display.
* Statusbar: toggle for network activity arrows.
* Merged Battery Bar.
* Inbuilt Lantern Music Player.
* Sync, Screenshot, HeadsUp, NavigBar On/Off tiles on top of CM
* Gesture Anywhere